The present invention relates to apparatus for automatically detecting the pitch of the individual notes of a musical composition which is represented in analog form by an electrical signal.
Apparatus for automatically detecting the pitch of musical notes is known in the art. Typically, this apparatus includes a plurality of band-pass filters connected in parallel. Such apparatus is illustrated and described, for example, in the U.S. Pat. No. 2,514,490 to John M. Hanert and the U.S. Pat. No. 3,277,245 to Imre Sponga.
Musical pitch detecting apparatus of this kind operates to detect the fundamentals of the individual notes of the musical composition. The threshold of detection is chosen sufficiently high so that only the fundamentals (and not the harmonics) of the individual notes of music will be detected.
This known apparatus will function properly provided that the musical notes which are to be detected are all of equal loudness. If, however, the music has a dynamic range that includes both soft and loud passages, the apparatus, if adjusted to detect the fundamentals of soft notes, will detect the harmonics of loud notes. In particular, if the threshold of detection is chosen sufficiently low so that the signals representing the fundamentals of soft notes exceed the threshold, the signals representing the harmonics of loud notes exceed this threshold as well.